There has been considerable recent interest in the incorporation of nanoscale components in lab-on-a-chip fluidic devices. This interest owes its origin to several advantages (and differences that may be advantageously leveraged) in moving from the micron scale to the nanoscale. These differences include, for example, double-layer overlap (DLO) and its effect on electro-osmosis and charge permselectivity, localized enhancement of electric fields, higher surface to volume ratios, confinement effects on large synthetic and bio-polymers, and the emerging importance of entropic effects. See, e.g., Yuan et al., Electrophoresis 2007, 28, 595-610; Schoch et al., Rev. Mod. Phys. 2008, 80, 839-883; and Kovarik et al., Anal. Chem, 2009, 81, 7133-7140. Historic examples of nanoscale devices include the use of porous media and gels in chromatographic separations and filtration membranes with nanoscale pores. See, e.g., Lerman et al., Biopolymers 1982, 21, 995-997; and Tong et al., M. Nano Lett. 2004, 4, 283-287. Recent efforts, however, have been focused on engineering geometrically well-defined conduits for fluid and analyte transport and seamlessly integrating them into devices. See, e.g., Volkmuth et al., Nature 1992, 358, 600-602; and Striemer et al., Nature 2007, 445, 749-753. The advantage of such regular structures is the relative simplicity of pressure and field gradients, fluid flow, and molecular motion contained within, in contrast to these properties in more tortuous networks. The capability to define, characterize, and easily model these systems can allow a better understanding of separation mechanisms and single molecule physics, for example. See, e.g., Volkmuth et al., Nature 1992, 358, 600-602; Reisner et al., Phys. Rev. Lett. 2005, 94, 196101; and Salieb-Beugelaar et al., Lab Chip 2009, 9, 2508-2523.
Recently FIB milling techniques have been described to form nanofluidic devices. See, Menard et al., Fabrication of Sub-5 nm Nanochannels in Insulating Substrates Using Focused Ion Beam Milling, Nano Lett. 2011, 11, 512-517 (published Dec. 20, 2010); and U.S. Provisional Patent Application Ser. No. 61/384,738, filed Sep. 21, 2010 (and related PCT Application PCT/US2011/052127), entitled, Methods, Systems And Devices For Forming Nanochannels, the contents of which are hereby incorporated by reference as if recited in full herein. In addition to FIB milling, a variety of other methods suitable for nanochannel fabrication can be used, including, for example, electron beam lithography, nanoimprint lithography, photolithography, templating or molding strategies, and other methods understood by one of ordinary skill in the art.
A number of nanofluidic devices have been proposed, including those with integrated miniature electrodes (nano- or micro-scale) for single-molecule sensing and/or nucleic acid sequencing. Alternatively, integrated devices consisting of entirely fluidic components can provide greater control of single-molecule transport and detection. See, Menard et al., A Device for Performing Lateral Conductance Measurements on Individual Double-Stranded DNA Molecules, ACS Nano 2012, 12, 9087-9094 (published Sep. 5, 2012); U.S. Provisional Patent Ser. No. 61/533,523, filed Sep. 12, 2011 (and corresponding pending PCT/US13/054,128), entitled, Devices with a Fluid Transport Nanochannel Intersected by a Fluid Sensing Nanochannel and Related Methods; and U.S. Provisional Patent Ser. No. 61/770,586, filed Feb. 28, 2013, entitled Nanofluidic Devices with Integrated Components for the Controlled Capture, Trapping, and Transport of Macromolecules and Related Methods of Analysis, the contents of which are hereby incorporated by reference as if recited in full herein. Such integration of components on a single monolithic device can enable new methods and systems that address current analysis needs in fields such as DNA sequencing and medical diagnostics.